Add Stevenjin8 as ztunnel maintainer

[Stevenjin8]

My ztunnel contributions

• No. 1 contributor in the last 6 months
• Multiple socket-fixes
  • Set NODELAY when accepting H2 connections ztunnel#615
  • Set timeouts and keepalive ztunnel#1641
  • Set keepalives on outbound connections ztunnel#1688
  • Set socket options outside trace! ztunnel#1689
• Better Testing
  • HBONE connections benches ztunnel#631
  • Use rustup llvm tools ztunnel#1387
• Multicluster
  • Double HBONE implementation for ambient multicluster ztunnel#1429
  • More baggage support ztunnel#1731
• A bunch of other stuff

I've also been reviewing PRs:

• No. 1 in submitted reviews in the last 6 months
• No. 1 in review comments in the last 6 months (though this chart seems wrong)
• Add x forwarded network header ztunnel#1728
• canonical wds service ztunnel#1704
• feat: implement crl support in ztunnel ztunnel#1660
• retain valid certs on fetch failures ztunnel#1567
• Better support for root certificates ztunnel#1510
• etc.

And active in issues:

• No. 1 in comments in the last 6 months (I'm also the only one)
• socket leak with time-wait ztunnel#1742
• Multiple ztunnel getting stuck in crashloopbackoff with error wrokloadmanager failed to start proxy: can't assign requested address ztunnel#1707
• Socket leak on inbound connection ztunnel#1694
• File descriptors leak ztunnel#1629
• Invalid peer certificate: BadSignature ztunnel#1613
• etc.

[kfaseela]

LGTM.. Leaving it to other steering members to approve who are active on ztunnel